x86-64: Move kernelstack from PDA to per-cpu.

Also clean up PER_CPU_VAR usage in xen-asm_64.S

tj: * remove now unused stack_thread_info()
    * s/kernelstack/kernel_stack/
    * added FIXME comment in xen-asm_64.S

Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

5 files changed, 11 insertions, 7 deletions

diff --git a/arch/x86/kernel/asm-offsets_64.c b/arch/x86/kernel/asm-offsets_64.c
index 4f7a210e1e58..cafff5f4a031 100644
--- a/arch/x86/kernel/asm-offsets_64.c
+++ b/arch/x86/kernel/asm-offsets_64.c
@@ -49,7 +49,6 @@ int main(void)
         BLANK();
 #undef ENTRY
 #define ENTRY(entry) DEFINE(pda_ ## entry, offsetof(struct x8664_pda, entry))
-        ENTRY(kernelstack); 
         ENTRY(oldrsp); 
         ENTRY(irqcount);
         DEFINE(pda_size, sizeof(struct x8664_pda));
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index b50e38d16888..06b6290088f4 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -889,6 +889,10 @@ DEFINE_PER_CPU(char *, irq_stack_ptr) =
         per_cpu_var(irq_stack) + IRQ_STACK_SIZE - 64;
 #endif
 
+DEFINE_PER_CPU(unsigned long, kernel_stack) =
+        (unsigned long)&init_thread_union - KERNEL_STACK_OFFSET + THREAD_SIZE;
+EXPORT_PER_CPU_SYMBOL(kernel_stack);
+
 void __cpuinit pda_init(int cpu)
 {
         struct x8664_pda *pda = cpu_pda(cpu);
@@ -900,8 +904,6 @@ void __cpuinit pda_init(int cpu)
         load_pda_offset(cpu);
 
         pda->irqcount = -1;
-        pda->kernelstack = (unsigned long)stack_thread_info() -
-                                 PDA_STACKOFFSET + THREAD_SIZE;
 
         if (cpu != 0) {
                 if (pda->nodenumber == 0 && cpu_to_node(cpu) != NUMA_NO_NODE)
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index d22677a66438..0dd45859a7a8 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -468,7 +468,7 @@ END(ret_from_fork)
 ENTRY(system_call)
         CFI_STARTPROC   simple
         CFI_SIGNAL_FRAME
-        CFI_DEF_CFA     rsp,PDA_STACKOFFSET
+        CFI_DEF_CFA     rsp,KERNEL_STACK_OFFSET
         CFI_REGISTER    rip,rcx
         /*CFI_REGISTER  rflags,r11*/
         SWAPGS_UNSAFE_STACK
@@ -480,7 +480,7 @@ ENTRY(system_call)
 ENTRY(system_call_after_swapgs)
 
         movq    %rsp,%gs:pda_oldrsp
-        movq    %gs:pda_kernelstack,%rsp
+        movq    PER_CPU_VAR(kernel_stack),%rsp
         /*
          * No need to follow this irqs off/on section - it's straight
          * and short:
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index e00c31a4b3c0..6c5f57602108 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -620,9 +620,9 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
         write_pda(oldrsp, next->usersp);
         percpu_write(current_task, next_p);
 
-        write_pda(kernelstack,
+        percpu_write(kernel_stack,
                   (unsigned long)task_stack_page(next_p) +
-                  THREAD_SIZE - PDA_STACKOFFSET);
+                  THREAD_SIZE - KERNEL_STACK_OFFSET);
 #ifdef CONFIG_CC_STACKPROTECTOR
         write_pda(stack_canary, next_p->stack_canary);
         /*
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 5854be0fb804..869b98840fd0 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -798,6 +798,9 @@ do_rest:
 #else
         clear_tsk_thread_flag(c_idle.idle, TIF_FORK);
         initial_gs = per_cpu_offset(cpu);
+        per_cpu(kernel_stack, cpu) =
+                (unsigned long)task_stack_page(c_idle.idle) -
+                KERNEL_STACK_OFFSET + THREAD_SIZE;
 #endif
         early_gdt_descr.address = (unsigned long)get_cpu_gdt_table(cpu);
         initial_code = (unsigned long)start_secondary;